1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a folder of a printing press.
2. Background Information
Web printing presses print a continuous web of material, such as paper. In a folder of the printing press, the continuous web then is cut into signatures in a cutting unit and folded.
One way to fold the resulting signatures is using a rotary blade folder, which includes a folding cylinder with tucker blades which provide a fold to the signature. The fold is forced by the tucker blade toward two rotating fold rolls, which grip the signature along the fold at a nip, set the fold and deliver the folded product, for example, to a fan unit.
Chapter 6 (pages 136 to 154) of the book xe2x80x9cNewspaper Pressesxe2x80x9d by William Braasch describes the two basic kinds of rotary blade folders: 2 to 1 folders and 3 to 2 folders. In a 2 to 1 rotary blade folder, two sets of tucker blades are spaced 180 degrees apart on the folding cylinder. A signature is held by pins spaced 90 degrees ahead of a tucker blade set and when the signature midpoint reaches the fold rollers, the tucker blade pushes the signature at the midpoint into the fold rollers so as to form the fold. Thus in a 2 to 1 folder, two sets of pins spaced 180 degrees apart are present, for holding edges of the products to be folded. In a 3 to 2 folder, three sets of pins spaced 120 degrees apart are present. Sets of tucker blades operate at a midpoint of a signature to produce a fold by pushing the midpoint into a pair of fold rollers.
Each set of tucking blades has a plurality of blades which must extend beyond the surface of the cylinder to produce the fold, and then retract to pass by the fold rollers. The blades of each set are spaced axially apart, and there can be, for example, four blades spaced axially along the folding cylinder. In order to provide for proper support of the signature to be folded on the folding cylinder, bands are located between the tucking blades so as to complete the circumference of the folding cylinder. For example, five bands can be spaced apart, with the tucking blades emerging through the bands. The bands can be adjusted to change an effective diameter of the folding cylinder to accommodate, for example, different signature thicknesses.
In, for example, the N1600 3 to 2 collect folder manufactured by Heidelberg Web Systems, Inc., the bands are attached to a block mechanism which can be adjusted by a motor. Each band is adjustable on the block mechanism to accommodate for differences between the bands and to provide for individual adjustment of each band.
However, adjusting the individual bands is difficult, time-consuming and can result in extensive work to achieve proper positioning of all of the bands. The adjustment mechanisms also may be prone to failure. Moreover, the single bands can collapse, causing malfunction of the folding cylinder.
An object of the present invention is to provide for a folding cylinder with a variable diameter which has improved strength. An additional or alternative object of the present invention is to provide a folding cylinder with an easily-adjustable variable diameter.
The present invention provides a rotary blade folder comprising two folding rollers and a folding cylinder having a cylinder body, a set of tucking blades and an expansion plate adjustable to change an effective diameter of the folding cylinder, the expansion plate having at least one aperture, the tucking blades fitting through the at least one aperture during a tucking operation so as to present a fold in a signature to the two folding rollers.
The expansion plate provides a stronger outer cylinder surface around the tucking blades, requires less assembly, and is easier to adjust. The plate also reduces air circulation and vacuum effects in the folding cylinder that can cause fold inaccuracies.
Preferably, the expansion plate is connected to the cylinder body at one edge by a pivot, and is connected to an actuating rod at another end. The actuating rod may be controlled by a motor to set the effective diameter.
Preferably, at least two sets of tucking blades are present, spaced evenly circumferentially about the folding cylinder, and at least two expansion plates are provided, one for each set of tucking blades.
The expansion plate preferably is made of spring steel, and may be of a grid construction for easier adjustment.
The present invention also provides a folding cylinder having a cylinder body, tucking blades and an expansion plate connected to an outer surface of the cylinder body and adjustable to change an effective diameter of the folding cylinder, the expansion plate having at least one aperture, the tucking blades fitting through the at least one aperture during a tucking operation so as to fold a signature.
The present invention also provides a method of folding a signature comprising the steps of:
gripping a signature about a folding cylinder so that the signature is over an expansion plate of the folding cylinder, the expansion plate having at least one aperture; and
folding the signature by passing tucking blades through the at least one aperture.
The method preferably includes passing a fold in the signature to two folding rolls to set the fold.
Preferably, the method also includes the step of adjusting the expansion plate as a function of a thickness of the signature. The adjusting step can include pivoting the expansion plate about a pivot. The pivoting can occur using a moving block mechanism, with the pivot at one edge of the expansion plate and the moving block mechanism at the other end. The block can be moved by a motor to set the proper effective diameter of the folding cylinder.